1/ Not always. Warmer temps help.
2/ No, don't go much lower though. 75 -even 80F will help you get thorough carbonation a bit quicker than say 65.
3/ Fresher is better with IPA. Just try not to let it be literally green - ie., if you filter out the hop particles thoroughly with a fine mesh bag or piece of women's hose then I say drink it as soon as it's carbed.